1. The invention relates to fatigue resisting structures made of powder metals, most particularly gas turbine disks.
2. Structures made of powder metals which are subjected to cyclic stresses often fail by fatigue cracks which initiate from flaws in the metal structure. Metallurgical examination of failed turbine disks often shows that fatigue cracks tend to initiate from ceramic inclusions and other flaws which were contained with the powder. Various techniques may be used to eliminate such ceramic inclusions, but to date the efficiency and cost thereof still leaves them somewhat wanting. Patent application Ser. No. 184,730, entitled "Fatigue Resistant Articles Made From Fine Metal Powder" by Slack et al, filed on even date hereof, discloses a process whereby the fatigue life of powder metal turbine disks is improved by using fine powder. This approach can involve increased cost in powder manufacture, since it is generally more difficult to make fine powder than coarse and the separated coarse fraction must be remelted or otherwise disposed of. The invention disclosed herein is in some respects an improvement on the Slack and Wentzell invention, and provides an alternate method for obtaining fatigue resisting turbine disks.